The Government has announced a full review of rail fares which could lead to some tickets falling in price but others rising.
The review was recommended in a Whitehall-commissioned review of rail industry costs by former Civil Aviation Authority chairman Sir Roy McNulty.
McNulty's study team says the fares review was necessary to simplify a complex system and to help the management of peak demand, with consideration given to possible changes to off-peak and saver regulation.
The review says: "The study does not recommend an increase in fares revenue overall, but instead envisages some fares increasing and others decreasing correspondingly, within the same revenue total."
This could mean some much sought-after off-peak fares, such as those operating on Friday evenings just as the rush-hour ends, could rise in price.
Trains leaving London on the West Coast line, for example, at around 7pm on Fridays are packed with those taking advantage of cheaper fares, while those leaving at the tail-end of the peak-fare period are comparatively empty.
Responding to the McNulty review, Transport Secretary Philip Hammond says the Department for Transport will conduct "a full review of fares policy, including addressing anomalies in the current system and the potential for much greater use of smart technology".
Rail customer watchdog Passenger Focus says this tinkering with off-peak fares represented a "leap in the dark", adding that "all the experience, all the history shows there will be more losers than winners".
UK rail fares are already the highest in Europe, with season ticket holders having to fork out for an average rise of the RPI rate of inflation plus 3% in January 2012.
In his review, McNulty says rail costs should be 20% to 30% lower than they were in 2008/09. He proposes cost-cutting measures which could deliver savings of between £700 million and £1 billion annually by 2019.
McNulty also concludes that rail wages are too high, rail working hours are too short and some ticket offices may have to be "done away with".